The human or animal olfactory system may be useful its ability to identify airborne molecules using a combinatorial response, in which a library of activated olfactory receptor-neurons provides a distinguishable pattern or “fingerprint” for each type of odorant (e.g., as described in Malnic et al. (1999) Cell 96: 713; M. Zarzo (2007) Biol. Rev. 82:455). Devices and systems that mimic the olfactory system, which may be referred to as “artificial noses”, may be useful for identification of vapor phase compounds. Conventional artificial noses for the detection of gas phase molecules may be based on modulation of electrical and/or gravimetric properties.
Although conventional optical sensing materials have been studied, incorporation of such materials into artificial noses may have been rare. Specific examples of such devices may include the use of conductive polymers and/or polymer composites.
Artificial nose devices based on the modulation of optical signals have been studied. For example, Dickinson et al. (Nature (1996) 382:697) describes using a fluorescence-based approach with a fiber optics array; Dickinson et al. ((1999) Anal Chem 71:2192) describes using self-encoded bead assisted detection; and Bowden et al. ((2005) Anal Chem 77:5583) describes the use of such a device for attomolar DNA detection. Another example study, by Rakow and Suslick (Nature (2000) 406:710) describes an artificial nose based on a colorimetric approach by using an array of metal porphyrins, in which each type of porphyrin may have shown a different coordination constant with the vapor analytes, and/or may have been thought to lead to unique colour change patterns upon binding of vapor phase ligands or solvatochromic induced effects. In another example, Janzen et al. ((2006) Anal. Chem. 78:3591) describes the incorporation of a larger variety of sensing species for discrimination of 100 volatile organic compounds.